A protective element has a body, an inner connection layer, an outer connection layer, a heating layer and a low-melting-point alloy layer. The body is made of a single insulation material. The inner and outer connection layers are formed on two upper and lower surfaces of the body. The low-melting-point alloy layer is formed on the upper surface of the body and is electrically connected to the inner connection layer. The heating layer is mounted inside the body and is electrically connected to the low-melting-point alloy layer by the inner connection layer. The outer connection layer is electrically connected to the low-melting-point alloy layer and the heating layer. The outer connection layer is soldered on a power circuit. When the power circuit encounters overcurrent, the heating layer is heated to fuse the low-melting-point alloy layer faster. Thus, power circuit is cut to protect the power circuit.

A protective element has a body, an inner connection layer, an outer connection layer, a heating layer and a low-melting-point alloy layer. The body is made of a single insulation material. The inner and outer connection layers are formed on two upper and lower surfaces of the body. The low-melting-point alloy layer is formed on the upper surface of the body and is electrically connected to the inner connection layer. The heating layer is mounted inside the body and is electrically connected to the low-melting-point alloy layer by the inner connection layer. The outer connection layer is electrically connected to the low-melting-point alloy layer and the heating layer. The outer connection layer is soldered on a power circuit. When the power circuit encounters overcurrent, the heating layer is heated to fuse the low-melting-point alloy layer faster. Thus, power circuit is cut to protect the power circuit.

A fuse including a fuse body, a fusible element disposed within the fuse body providing an electrically conductive pathway extending between a first end of the fuse body and a second end of the fuse body, and a heat shield disposed within the fuse body intermediate an interior surface of the fuse body and an exterior surface of the fuse body for mitigating heat flow therebetween.

A fuse device includes a fuse element and a cooling member, wherein the fuse element includes a low thermal conductivity portion having a relatively low thermal conductivity in which an interrupting portion that is blown out by heat is separated from the cooling member, and a high thermal conductivity portion having a relatively high thermal conductivity, provided in a portion other than the interrupting portion, and in contact with or close to the cooling member.

A fuse element as well as a fuse device and protective device using the same which are capable of suppressing generation of defects such as cracks in a high melting point metal layer, maintaining good conduction, and maintaining blowout properties. The fuse element includes a laminated low melting point metal layer and high melting point metal layer and at least one peak among peaks in an X-ray diffraction spectrum (2) of a surface of the high melting point metal layer has a full width at half maximum of 0.15 degrees or less.

To produce a cost-effective fuse in chip design, which is applied to a carrier substrate made of a Al.sub.2O.sub.3 ceramic having a high thermal conductivity, and which is provided with a fusible metallic conductor and a cover layer, in which the melting point of the metallic conductor may be defined reliably, it is suggested that an intermediate layer having low thermal conductivity be positioned between the carrier substrate and the metallic conductor, the intermediate layer being formed by a low-melting-point inorganic glass paste applied in the screen-printing method or an organic intermediate layer applied in island printing. Furthermore, a method for manufacturing the fuse is specified.

A fuse element as well as a fuse device and protective device using the same which are capable of suppressing generation of defects such as cracks in a high melting point metal layer, maintaining good conduction, and maintaining blowout properties. The fuse element includes a laminated low melting point metal layer and high melting point metal layer and at least one peak among peaks in an X-ray diffraction spectrum (2) of a surface of the high melting point metal layer has a full width at half maximum of 0.15 degrees or less.

A fuse device includes a fuse element and a cooling member, wherein the fuse element includes a low thermal conductivity portion having a relatively low thermal conductivity in which an interrupting portion that is blown out by heat is separated from the cooling member, and a high thermal conductivity portion having a relatively high thermal conductivity, provided in a portion other than the interrupting portion, and in contact with or close to the cooling member.